Portable terminals are evolving into multimedia communication devices that provide not only a voice call service but also a data transmission service and various additional services. In addition, with an increase in the number of services provided by portable terminals, an increasing interest taken in User Interface (UIs) for controlling portable terminals.
A touchscreen-based portable terminal includes a proximity sensor for preventing a malfunction during a call. For example, when a user calls with a touchscreen-based portable terminal, the user touches the touchscreen-based portable terminal to his ear or cheek. In this case, the touchscreen-based portable terminal may malfunction due to an undesired key input caused by the touch to the user's ear or cheek. Accordingly, if detecting the proximity (or approach) of the user (i.e., the coverage of its receiver) by the proximity sensor, the touchscreen-based portable terminal enables a screen lock mode to prevent the malfunction. Also, if detecting the withdrawal of the user from the touchscreen-based portable terminal by the proximity sensor during the screen lock mode, the touchscreen-based portable terminal disables the screen lock mode.
Typically, the proximity sensor includes a photodiode as illustrated in FIG. 1.
FIG. 1 block illustrates a conventional proximity sensor.
Referring to FIG. 1, a proximity sensor 100 includes a light emitting unit 102 and a light receiving unit 104.
The proximity sensor 100 determines the proximity (or approach) of an object on the basis of the quantify of light that is received by the light receiving unit 104 after being emitted by the light emitting unit 102 and reflected by the object (hereinafter referred to as a light-receiving quantity).
If a portable terminal uses a proximity sensor, the portable terminal sets a reference light-receiving quantity for determining the proximity (or approach) of an object. Accordingly, if a light-receiving quantity detected by a light receiving unit of the proximity sensor is larger than the reference light-receiving quantity, the portable terminal determines that the object has approached thereto. Alternatively, if the light-receiving quantity detected by the light receiving unit of the proximity sensor is smaller than the reference light-receiving quantity, the portable terminal determines that the object has not approached thereto. Herein, the reference light-receiving quantity is set on the basis of a reference proximity detection distance of the object from the proximity sensor, at which the proximity sensor detects that the object has approached thereto.
In general, reflectors have different light reflectances according to their colors. For example, reflectors have different light reflectances according to their colors as shown in Table 1 below.
TABLE 1reflectance3%9%12%18%24%36%48%93%colorBlackCobaltEmeraldGreyLightLight GreyLightWhiteVioletBrownGreenGreenYellowYellowBlueOrangeSky BlueLight SkyRedPinkLight PinkLight Violet
If reflectors have different light reflectances as described above, even if the reflectors are located at the same distance, a light-receiving quantity detected by a light receiving unit of a proximity sensor varies according to the light reflectance of each reflector.
If the reference light-receiving quantity is set on the basis of a white object, because a black object has a low light reflectance than the white object, the proximity sensor may fail to detect the proximity of the black object or its proximity detection distance may decrease.
Therefore, a portable terminal mounted with a proximity sensor requires a scheme for adaptively detecting the proximity of a reflector according to the light reflectance of the reflector.